1. Field of Invention
The present invention relates to a speech recognition method, a storage medium storing a speech recognition program, and a speech recognition apparatus capable of achieving a high accuracy of recognition even under an environment where various background noises are present.
2. Description of Related Art
In recent years, devices incorporating speech recognition functionality have been widely used. The devices are used under various environments, and in many cases under environments including a large amount of noise.
In such cases, obviously, countermeasures must be taken against noise. Examples of noise include, stationary noises such as the sound of an automobile and the sound of an air conditioner. Speech recognition methods described below have been used for performing speech recognition under an environment where such stationary noises are present.
As a first example, speech recognition may be performed by superposing noise data obtained from the stationary noises described above on speech data taken under a noise-free environment, creating an acoustic model by learning the speech data, and using the acoustic model.
As a second example, speech recognition may be performed, by a spectral subtraction method. According to this speech recognition method, the noise component is eliminated from input speech data, and a speech recognition is performed on the speech data which has undergone the noise elimination. In this case as well, similarly to the above, noise data obtained from the stationary noises are superposed on speech data taken under a noise-free environment, the noise is eliminated by the spectral subtraction method from the speech data, an acoustic model is created by learning the speech data which has undergone the noise elimination, and a speech recognition is performed based on the acoustic model.